New : when installation of the section is a new route (a new link for example)

Renewed : when an overhead section is replaced with an overhead section or when an underground section is replaced with an underground section

Buried : when an overhead section is replaced with an underground section

Scrapped : when the section is physically retired from the network

Other changes : These are all the unrecorded length variations in new and scrapped sections. These are mainly sections placed in reserve (disconnected from the network but still in place), but also corrections of errors and length